LXT9863 datasheet(21/56 Pages) INTEL

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Advanced 10/100 Unmanaged Repeater — LXT9883/9863

Datasheet

Document #: 249115

Revision #: 003

Rev. Date: 08/07/01

Each supply input should be decoupled to ground. Refer to Table 6 on page 15 for power and

ground pin assignments, and to the "General Design Guidelines” on page 32..

3.5.2

Clock

A stable, external 25MHz reference clock source (TTL) is required to the CLK25 pin. The

reference clock is used to generate transmit signals and recover receive signals. A crystal-based

clock is recommended over a derived clock (i.e., PLL-based) to minimize transmit jitter. Refer to

Table 18 on page 37 for a list of recommended oscillators and to Table 21 on page 44 for clock

timing requirements.

3.5.3

Bias Resistor

The RBIAS input requires a 22.1 k

Ω, 1% resistor connected to ground.

3.5.4

Reset

At power-up, the reset input must be held Low until VCC reaches at least 3.15V. A buffer should be

used to drive reset if there are multiple LXT98x3 devices. The clock must be active.

3.5.5

IRB Bus Pull-ups

Even when the LXT98x3 is used in a stand-alone configuration, pull-up resistors are required on

the IRB signals. See Figure 16 and Figure 17 on page 43.

3.6

LED Operation

The LXT98x3 drives the most commonly used LEDs directly (see "Direct Drive LEDs” on

page 24.). The less frequently used LEDs are optionally driven via a serial bus to inexpensive

Serial-to-Parallel devices (see “Serial LEDs” on this page).

3.6.1

LEDs at Start-up

For approximately 2 seconds after the LXT98x3 is reset, all LEDs are driven to the ON state. This

start-up routine is an LED check.

100 Mbps IRB

10 Mbps IRB

IR100CFS

IR10DAT

IR100CFSBP

IR10ENA

IR100DV

IR10COL

IR100CLK

IR10CFS

IR10COLBP

IR10CFSBP

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